1. Field of the Invention
The present invention is concerned with a procedure for attaching ribs to pipes which preferably have a cross-section that is not circular in form.
2. Discussion of the Prior Art
The production of, for instance, accelerator jet-pipes with any desired pipe cross-section and a smooth inner surface, which are stable when exposed to atmospheric air pressure despite low weight and thin pipe walls, is a technical problem for the following reasons:
The brazing of stiffening ribs onto the pipes in a brazing furnace under vacuum or inert gas succeeds only if the brazing gap between the stiffening ribs and the pipe is very small at the brazing temperature, i.e., smaller than 0.1 mm. The problem was previously solved by mechanically expanding the pipe by means of a spreading tool locally prior to brazing and thus achieving attachment of the pipe to the ribs. However, a mechanical or hydraulic mechanical spreading tool is a very expensive item. Further, a spreading tool for pipe cross sections other than circular either can only be used with quite considerable effort or cannot be used for this procedure. Also, because of the mechanical spreading which occurs prior to brazing there is no guarantee that the narrow brazing gap is still maintained during brazing. One example of this is caused by the deformation of the pipe during high brazing temperatures.
In order to guarantee success during the brazing of the ribs, the brazing gaps should be kept as small as possible. However, because of procedural constraints, the holes and negative forms on the ribs can be made very exactly but the pipe form and the corresponding positive form can only be made with variations of greater than or equal to 0.1 mm. Furthermore, with the choice of different materials preserving small brazing gaps is difficult to realize. The outer circumference of the jet-pipe body and the circumference of the corresponding opening in the ribs have to be in exact agreement. Mistakes would make attachment of the ribs on the pipe body impossible, and the consequence would be undesired scratch marks into which the soldering material would penetrate and could not be stopped.
For these reasons, on one hand, a large assembly gap prior to brazing and, on the other hand, during the moment of brazing, a brazing gap as small as possible and specifically which is less than or equal to 0.05 mm are desirable.